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1.
The activity and stability of non-precious metal catalysts (NPMCs) for the oxygen reduction reaction (ORR) in both acid and alkaline electrolytes were studied by the rotating disk electrode technique. The NPMCs were prepared through the pyrolysis of cobalt-iron-nitrogen chelate followed by combination of pyrolysis, acid leaching, and re-pyrolysis. In both environments, the catalysts heat-treated at 800-900 °C exhibited relatively high activity. Particularly, an onset potential of 0.92 V and a well-defined limiting current plateau for the ORR was observed in alkaline medium. The potential cycling stability test revealed the poor stability of NPMCs in acid solution with an exponential increase in the performance degradation as a function of the number of potential cycling. In contrast, the NPMCs demonstrated exceptional stability in alkaline solution. The numbers of electron transferred during the ORR on the NPMCs in acid and alkaline electrolytes were 3.65 and 3.92, respectively, and these numbers did not change before and after the stability test. XPS analysis indicated that the N-containing sites of catalysts are stable before and after the stability test when in alkaline solution but not in acid solution.  相似文献   

2.
The cost of platinum is one of the major obstacles in the commercialization of proton exchange membrane fuel cells. Non-precious metal catalysts (NPMC) as an inexpensive substitute for platinum have been viewed as the only long-term solution to the problem. In this paper, we introduce new precursors used to synthesize NPMC active sites through metal-assisted polymerization of nitrogen-containing, aromatic molecules. Results of electrochemical characterization, which was performed in a real fuel cell environment, with emphasis on the activity of the catalyst are presented. Catalytic activity among the highest in the NPMC area was obtained when using 4-nitroaniline as a precursor.  相似文献   

3.
Co based catalyst were evaluated for oxygen reduction (ORR) in liquid KOH and alkaline anion exchange membrane fuel cells (AAEMFCs). In liquid KOH solution the catalyst exhibited good performance with an onset potential 120 mV more negative than platinum and a Tafel slope of ca. 120 mV dec−1. The hydrogen peroxide generated, increased from 5 to 50% as the electrode potential decreased from 175 to −300 mV vs. SHE.In an AAEMFC environment, one catalyst (GP2) showed promising performance for ORR, i.e. at 50 mA cm−2 the differences in cell potential between the stable performance for platinum (more positive) and cobalt cathodes with air and oxygen, were only 45 and 67 mV respectively. The second catalyst (GP4) achieved the same stable power density as with platinum, of 200 and 145 mW cm−2, with air at 1 bar (gauge) pressure and air (atm) cathode feed (60 °C), respectively. However the efficiency was lower (i.e. cell voltage was lower) i.e. 40% in comparison to platinum 47.5%.  相似文献   

4.
Tellurium (Te)-modified carbon catalyst for oxygen reduction reaction was prepared through chemical reduction of telluric acid followed by the pyrolysis process at elevated temperatures. The catalyst was found to be active for oxygen reduction reaction. High-temperature pyrolysis plays a crucial role in the formation of the active sites of the catalysts. When the pyrolysis was conducted at 1000 °C, the catalyst exhibited the onset potential for oxygen reduction as high as 0.78 V vs. NHE and generated less than 1% H2O2 during oxygen reduction. The performance of the membrane–electrode assembly prepared with the Te-modified carbon catalyst was also evaluated.  相似文献   

5.
The alkaline anion exchange membrane fuel cell (AEMFC) is one of the green solutions for the growing need for energy conversion technologies. For the first time, we propose a natural shungite based non-precious metal catalyst (NPMC) as an alternative cathode catalyst to Pt-based materials for AEMFCs application. The Co and Fe phthalocyanine (Pc)-modified shungite materials were prepared via pyrolysis and used for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) studies. The most promising ORR performance was observed in alkaline media for FePc-modified and acid-leached shungite-based NPMC material. The catalysts were also evaluated as cathode materials in a single cell AEMFC and peak power densities of 232 and 234 mW cm?2 at 60 °C using H2 and O2 gases at 100% RH were observed for CoPc- and FePc-modified acid-treated materials, respectively.  相似文献   

6.
An improved synthesis scheme of non-precious metal N-doped carbon catalysts for oxygen reduction reaction is reported. The non-precious metal N-doped carbon catalysts were prepared by pyrolysis of the mixture (phenol resin, Ketjen black carbon support and cobalt phenanthroline complex). The drastic improvement of distribution state of Ketjen black supported non-precious metal N-doped carbon catalysts was observed by means of transmission electron microscopy (TEM). In addition, the non-precious metal N-doped carbon catalyst synthesized with Ketjen black carbon support showed much higher oxygen reduction reaction (ORR) activity relative to unsupported non-precious metal N-doped carbon catalyst in O2-saturated 0.5 mol l−1 H2SO4 at 35 °C. Moreover, the highest ORR activity was obtained with addition of optimum amount of Ketjen black carbon support was thirtyfold compared to unsupported non-precious metal N-doped carbon catalyst at 0.7 V. Similarly, the performance of a polymer electrolyte fuel cell (PEFC) using the non-precious metal N-doped carbon catalyst as the cathode electrode catalyst was obviously better than that of the non-precious metal N-doped carbon catalyst before optimization. Microstructure, specific surface area and surface composition of the non-precious metal N-doped carbon catalysts were analyzed by XRD, XPS and BET measurement with nitrogen physisorption, respectively.  相似文献   

7.
Hydrogen–oxygen fuel cells using an alkaline anion exchange membrane were prepared and evaluated. Various non-platinum catalyst materials were investigated by fabricating membrane-electrode assemblies (MEAs) using Tokuyama membrane (# A201) and compared with commercial noble metal catalysts. Co and Fe phthalocyanine catalyst materials were synthesized using multi-walled carbon nanotubes (MWCNTs) as support materials. X-ray photoelectron spectroscopic study was conducted in order to examine the surface composition. The electroreduction of oxygen has been investigated on Fe phthalocyanine/MWCNT, Co phthalocyanine/MWCNT and commercial Pt/C catalysts. The oxygen reduction reaction kinetics on these catalyst materials were evaluated using rotating disk electrodes in 0.1 M KOH solution and the current density values were consistently higher for Co phthalocyanine based electrodes compared to Fe phthalocyanine. The fuel cell performance of the MEAs with Co and Fe phthalocyanines and Tanaka Kikinzoku Kogyo Pt/C cathode catalysts were 100, 60 and 120 mW cm−2 using H2 and O2 gases.  相似文献   

8.
Low temperature fuel cells, such as the proton exchange membrane (PEM) fuel cell, have required the use of highly active catalysts to promote both the fuel oxidation at the anode and oxygen reduction at the cathode. Attention has been particularly given to the oxygen reduction reaction (ORR) since this appears to be responsible for major voltage losses within the cell. To provide the requisite activity and minimse losses, precious metal catalysts (containing Pt) continue to be used for the cathode catalyst. At the same time, much research is in progress to reduce the costs associated with Pt cathode catalysts, by identifying and developing non-precious metal alternatives. This review outlines classes of non-precious metal systems that have been investigated over the past 10 years. Whilst none of these so far have provided the performance and durability of Pt systems some, such as transition metals supported on porous carbons, have demonstrated reasonable electrocatalytic activity. Of the newer catalysts, iron-based nanostructures on nitrogen-functionalised mesoporous carbons are beginning to emerge as possible contenders for future commercial PEMFC systems.  相似文献   

9.
Nitrogen-modified carbon-based catalysts for oxygen reduction were synthesized by modifying carbon black with nitrogen-containing organic precursors. The electrocatalytic properties of catalysts were studied as a function of surface pre-treatments, nitrogen and oxygen concentrations, and heat-treatment temperatures. On the optimum catalyst, the onset potential for oxygen reduction is approximately 0.76 V (NHE) and the amount of hydrogen peroxide produced at 0.5 V (NHE) is approximately 3% under our experimental conditions. The characterization studies indicated that pyridinic and graphitic (quaternary) nitrogens may act as active sites of catalysts for oxygen reduction reaction. In particular, pyridinic nitrogen, which possesses one lone pair of electrons in addition to the one electron donated to the conjugated π bond, facilitates the reductive oxygen adsorption.  相似文献   

10.
Pd-coated manganese dioxide catalysts (Pd@MnO2) were synthesized by depositing Pd on the surface of β-MnO2 nanorod particles in aqueous solutions at room temperature. TEM, XRD and electrochemical characterizations indicated that the MnO2 nanorods were successfully coated with Pd particles when the Pd weight percentage was more than 4.6%. The activities of the Pd@MnO2 catalysts for oxygen reduction reaction (ORR) were investigated using a rotating disk electrode (RDE) and a rotating ring-disk electrode (RRDE). The ORR onset potentials on the Pd@MnO2 catalyst shifted positively for more than 250 mV compared with the MnO2 catalyst without Pd coatings. Both the ORR onset potentials and the limiting current density obtained by the RDE measurements on the Pd@MnO2 catalysts were close to those on the Pd black catalyst. The mass activity of the Pd@MnO2 catalysts (normalized by Pd mass) was 2.5 times higher than that of the Pd black catalyst. Based on the Tafel slopes of the Pd@MnO2 catalysts (which is about 60 mV dec−1 at low overpotentials), and based on the fact that the activation energies of the Pd@MnO2 catalysts are very close to the activation energies of the Pd catalysts, one may conclude that the small amount of Pd coating provides the primary ORR activity of the Pd@MnO2 catalysts.  相似文献   

11.
For application in a microbial fuel cell (MFC), transition metal and nitrogen co-doped nanocarbon catalysts were synthesised by pyrolysis of multi-walled carbon nanotubes (MWCNTs) in the presence of iron- or cobalt chloride and nitrogen source. For the physicochemical characterisation of the catalysts, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) was used. The results obtained by rotating disk electrode (RDE) method showed an extraordinary electrocatalytic activity of these catalysts towards oxygen reduction reaction (ORR) in neutral media, which was also confirmed by the MFC results. The Co-N-CNT and Fe-N-CNT cathode catalysts exhibited maximum power density of 5.1 W m?3 and 6 W m?3, respectively. Higher ORR activity and improved electric output in the MFC could be attributed to the formation of the active nitrogen-metal centers. All findings suggest that these materials can be used as potential cathode catalysts for ORR in MFC to replace expensive noble-metal based materials.  相似文献   

12.
Doped carbon nanostructures as non-precious metal (NPM) catalysts for oxygen reduction reaction (ORR) in acid medium are mainly synthesized using 5, 10, 15, 20-tetrakis (4-methoxyphenyl)-porphyrin-Fe (III) chloride (Fe-TMPP) as doping and carbon sources. In this study, the doped carbon nanostructures used as cathode NPM catalysts for ORR are prepared using a mixture of iron phthalocyanine (FePc) and arginine as doping and carbon sources. The morphology and composition of the as-prepared samples are characterized using field-emission scanning electron microscopy, field-emission transmission electron microscopy, and energy dispersive X-ray (EDX) spectroscopy. The crystal and pore structures are analyzed using X-ray diffraction method, Raman spectroscopy, and nitrogen adsorption/desorption method. The sample prepared using a precursor mixture with a proper ratio of FePc and arginine exhibits significantly superior ORR performance, i.e. high specific activity, enhanced half-wave potential, and improved stability in an acid medium, as even compared to a commercial Pt/C. The improved ORR properties is mainly attributed to high portion of pyridinic N state with a relatively high specific surface area, which can result from the FePc precursor surrounded by the fused arginine.  相似文献   

13.
Highly active and stable carbon composite catalysts for oxygen reduction in PEM fuel cells were developed through the high-temperature pyrolysis of Co–Fe–N chelate complex, followed by the chemical post-treatment. A metal-free carbon catalyst was used as the support. The carbon composite catalyst showed an onset potential for oxygen reduction as high as 0.87 V (NHE) in H2SO4 solution, and generated less than 1% H2O2. The PEM fuel cell exhibited a current density as high as 0.27 A cm−2 at 0.6 V and 2.3 A cm−2 at 0.2 V for a catalyst loading of 6.0 mg cm−2. No significant performance degradation was observed over 480 h of continuous fuel cell operation with 2 mg cm−2 catalyst under a load of 200 mA cm−2 as evidenced by a resulting cell voltage of 0.32 V with a voltage decay rate of 80 μV h−1. Materials characterization studies indicated that the metal–nitrogen chelate complexes decompose at high pyrolysis temperatures above 800 °C, resulting in the formation of the metallic species. During the pyrolysis, the transition metals facilitate the incorporation of pyridinic and graphitic nitrogen groups into the carbon matrix, and the carbon surface doped with nitrogen groups is catalytically active for oxygen reduction.  相似文献   

14.
Alkaline fuel cells suggest solution for the problems of low methanol oxidation kinetics and methanol crossover, which are limiting the development of direct methanol fuel cells. In this work, a novel anion exchange membrane, quaternized poly(aryl ether oxadiazole), was prepared through polycondensation, grafting and quaternization. The ionic conductivity of as-synthesized anion exchange membrane can reach up to 2.79 × 10−2 S/cm at 70 °C. The physical and chemical stability of the anion exchange membranes could also meet the requirement for alkaline direct methanol fuel cells.  相似文献   

15.
Transition metal-nitrogen-carbon (MNC) based non-platinum metal catalysts obtained by pyrolysis of a transition metal, carbon and nitrogen sources were viewed as an inexpensive substitute for the platinum-based electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. Due to the pyrolysis step involved in synthesizing MNC catalysts, the exact active site structure responsible for ORR was not conclusively identified thereby limiting the efforts of scientists in identifying effective synthetic routes to achieve highly active MNC catalysts with required active site structure and site density. To alleviate the lack of clarity on the active site structure of MNC catalysts, as a substitute, copper, and cobalt-based metal-organic frameworks and complexes were synthesized recently and shown to be ORR active. In this study, we have synthesized an Iron(III) chloride-benzotriazole ([FeCl3(btaH)2]) adduct and demonstrated its ORR activity in alkaline medium, which primarily reduces oxygen by 4-electron reduction pathway. Single crystal XRD characterization revealed the crystal structure of [FeCl3(btaH)2] unambiguously. The ORR onset potential, Tafel slopes, and methanol tolerance ability of [FeCl3(btaH)2] were compared against commercial 20 wt% Pt/C. [FeCl3(btaH)2] adduct shows complete methanol tolerance and ORR onset potential of 0.89 V vs. RHE, which is highest among the unpyrolyzed metal-organic frameworks/complexes.  相似文献   

16.
In this study, we reported a comparison study between the performance of the commercial non-noble metal cathode electrode (made by Hypermec™ K14 catalyst - provided by Acta S.p.A.) and cathode electrode containing 10 wt% Pt/C, in the alkaline direct ethanol fuel cell (ADEFC) under different conditions.Further electrochemical investigations have been done by RDE and driven mode cell to compare the intrinsic activity and selectivity of 10 wt% Pt/C and Hypermec™ K14 transition metals cathode catalysts. It is worthwhile to point out that Hypermec™ K14 cathode catalyst shows a remarkable selectivity to oxygen reduction and it has a superior intrinsic activity in oxygen reduction reaction (ORR) especially in terms of volumetric current density (A/cm3). Test results of active DEFC made by non-noble cathode catalyst showed superior performance compared to the cell made by 10 wt% Pt/C cathode catalysts in terms of power density and OCV at 60 °C and ambient pressure. This result is related to the higher ORR kinetic of non-noble metal cathode catalyst in alkaline media.  相似文献   

17.
In this study, a highly ion-conductive and durable porous polymer electrolyte membrane based on ion solvating polybenzimidazole (PBI) was developed for anion exchange membrane fuel cells (AEMFCs). The introduction of porosity can increase the attraction of electrolytic solutions (e.g., potassium hydroxide (KOH)) and ion solvation, which results in the enhancement of PBI's ionic conductivity. The morphology, thermo-physico-chemical properties, ionic conductivity, alkaline stability, and the AEMFC performance of KOH-doped PBI membranes with different porosities were characterized. The ionic conductivity and AEMFC performance of 70 wt.% porous PBI was about 2 times higher than that of the commercially available Fumapem® FAA. All KOH-doped porous PBI membranes maintained their ionic conductivity after accelerated alkaline stability testing over a period of 14 days, while the commercial FAA degraded just after 3 h. The excellent performance and good durability of KOH-doped porous PBI membrane makes it a promising candidate for AEMFCs.  相似文献   

18.
The effect of the metal for the oxygen reduction reaction (ORR) in acid medium with non-precious metal catalysts has been investigated. A series of non-precious metal catalysts with typical formulation M/N/C with M being Mn, Co or Fe have been prepared by incorporating N onto an active carbon matrix by means of thermal treatments under inert atmospheres. The N-containing active carbons were further treated with the M-containing precursors based upon Mn, Co or Fe phthalocyanines and thermally treated under inert atmosphere. The performance for the ORR in acid medium of all of the catalysts has been evaluated by means of electrochemical techniques. The activity, both in terms of onset potential for the ORR and maximum current density at representative potentials between 900 and 700 mV follows the trend Fe > Co > Mn. In addition, the performance of the Fe-based catalysts obtained during the different stages of the catalyst preparation has been also evaluated. The catalysts obtained after the pyrolysis step are the only ones showing measurable rates for the ORR. Although the amount of N and Fe incorporated onto the carbon matrix decreases the pyrolysis treatment, this treatment leads to the formation of the real active sites for the ORR irrespectively of the nature of the transition metal.  相似文献   

19.
    
The use of Pt-based cathode catalyst materials hinders the widespread application of anion exchange membrane fuel cells (AEMFCs). Herein, we present a non-precious metal catalyst (NPMC) material based on pyrolysed Fe and Co co-doped electrospun carbon nanofibres (CNFs). The prepared materials are studied as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts in alkaline and acidic environments. High activity towards the ORR in alkaline solution indicated the suitability of the prepared NPMCs for the application at the AEMFC cathode. In the AEMFC test, the membrane-electrode assembly bearing a cathode with the nanofibre-based catalyst prepared with the ionic liquid (IL) (Fe/Co/IL–CNF–800b) showed the maximum power density (Pmax) of 195 mW cm−2, which is 78% of the Pmax obtained with a commercial Pt/C cathode catalyst. Such high ORR electrocatalytic activity was attributed to the unique CNF structure, high micro-mesoporosity, different nature of nitrogen species and metal-Nx active centres.  相似文献   

20.
Highly efficient, cost-effective and environmental-friendly electrocatalysts play a crucial role in oxygen reduction reaction (ORR) for fuel cells and metal-air batteries. Herein, a series of hybrids comprising of NiCo alloy, metal oxides and carbon black were readily prepared by a one-pot pyrolysis approach and employed as efficient ORR electrocatalysts in the alkaline media. Different amounts of Ketjen Black EC 300J (EC) with a large mesoporous area and exceptional electrical conductivity were directly added to synthesize the hybrids. Among the hybrids tested, the NC-MMO-EC-3 (where NC stands for NiCo alloy and MMO for mixed metal oxides) with an appropriate amount of EC displayed the best ORR electrochemical activity. The enhanced activity of the NC-MMO-EC-3 could be attributed to the conductivity improved by EC, the high dispersion of MMO and NC on EC support, and the beneficial interaction among those three components.  相似文献   

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